Obstructive sleep apnea (OSA) is a common problem, and cognitive deficits associated with OSA have been documented in many studies. While evidence suggests that cognitive dysfunction in OSA may be related to hypoxemia-induced damage to the frontal lobes and/or sub cortical areas, such a connection has not been directly established. Rather, it has been inferred from the finding that these deficits do not improve following treatment with continuous positive airway pressure (CPAP). The proposed study will attempt to directly connect both general and specific executive function deficits in OSA to the effects of intermittent nocturnal hypoxemia by comparing OSA subjects who differ in the severity of apnea-hypopnea associated hypoxemia, but who have been matched on other important indicators of disease severity (i.e., AHI, arousal index) on a number of neuropsychological measures of executive function. Establishing a direct connection between intermittent nocturnal hypoxemia and permanent cognitive deficits in OSA will emphasize the importance of early detection and treatment. Additionally, further clarifying the specific executive function deficits associated with OSA will allow for the development of cognitive rehabilitation strategies to assist these patients in better compensating for their cognitive difficulties.